This invention relates to a process for the assembly of radial tire components and to an apparatus for practicing said process.
In the evolutionary course of developing and producing the state of the art radial ply pneumatic tire, those skilled in the art, have created a tire structure consisting generally of two major sub-assemblies or two distinct groups of components, depending on the assembly process.
The first sub-assembly, referred to herein as the "first stage carcass" consists of one or more body plys of rubber coated cord, a pair of axially spaced parallel beads and layers of rubber that will comprise the sidewall stock of the carcass. These tire elements are assembled and consolidated on a cylindrical building drum so that the first stage carcass sub-assembly consists of one or more body plys which, in the case of a radial tire, the body ply cords are essentially parallel to the rotational axis of the building drum and the first stage carcass assembled thereon; the two beads are anchored to the opposing axial extremities of the cylindrical first stage carcass, said beads being parallel one to the other and coaxial with the rotational axis of said first stage carcass; and the layers of sidewall stock are circumferentially consolidated to the outer surface of the first stage carcass, axially disposed one from the other and adjacent to one of the beads.
Upon completion of the first stage carcass sub-assembly, it is then transformed from its cylindrical shape to that of a toroid so that the radial body cords, essentially parallel to the rotational axis are made to assume the configuration of meridians to said rotational axis.
Completion of the green radial tire carcass is then accomplished by consolidating one or more relatively non-extensible belts of suitable cord to the outer equatorial circumference of the toroid and finally symmetrically disposing about the same equatorial circumference a band of tread stock. After the belts and tread stock are consolidated with the toroidal first stage carcass, the finished green radial tire carcass is removed from the building machine and disposed in a suitable mold for final shaping and vulcanization of the various rubber components, thereby forming a cured tire.
The sub-assembly consisting of one or more belts and the tread stock will hereinafter be referred to as the "belt-tread stock assembly".
Conversion of the cylindrical first stage carcass to the toroidal shape and attaching the belt-tread components thereon is achieved in a variety of ways, the more conventional being:
(a) Assembly of the first stage carcass components on a holding drum that is capable of causing the consolidated cylindrical shaped first stage carcass to be transformed into a toroidal shape and then completion of the green radial tire carcass by attaching equatorially thereon the belt and tread stock elements.
This is usually referred to as the "single stage process" of green radial tire assembly.
(b) Assembly of the first stage carcass on a conventional collapsable building drum that is incapable of transforming a cylindrical carcass to toroidal shape, and, upon completion of that cylindrical sub assembly, transferring same to a different drum or holding means whereby said first stage carcass is held and manipulated during its transformation to toroidal shape and the assembly of belts and tread stock thereon.
Appropriately, this is generally referred to as the "two stage process".
The number of conventional construction process options is further expanded by the alternatives of either assembling and consolidating the belts and tread stock directly on the toroidal first stage carcass or the assembly and consolidation of the belts and tread stock on a separate drum and then conveying that belt-tread sub-assembly to a coaxial position with the toroidal shaped first stage carcass where upon said toroidal first stage carcass is caused to be further expanded into circumferential contact and consolidation with the inner surface of the belt-tread sub-assembly.
The quality of the completed radial ply tire requires that dimensionally accurate components are precisely assembled and that such precision of dimension and assembly be retained and protected throughout the balance of the tire manufacturing process.
State of the art second stage radial tire building machines generally consist of a bed upon which there is axially aligned and mounted at opposite ends thereof a head stock holding and capable of rotational manipulation of a collapsible belt building drum and, on the opposite end, a tail stock capable of supporting a first stage carcass whereby said first stage carcass is transformed from cylindrical to toroidal shape, united with a belt-tread stock assembly and then rotated about its axis while final consolidation is accomplished by stitching.